FLUXLESS FLIP CHIP INTERCONNECTION

摘要

A flip chip method of joining a chip and a substrate is described. A thermo-compression bonder is utilized to align the chip and substrate and apply a contact force to hold solder bumps on the substrate against metal bumps on the chip. The chip is rapidly heated from its non-native side by a pulse heater in the head of the bonder until the re-flow temperature of the solder bumps is reached. Proximate with reaching the re-flow temperature at the solder bumps, the contact force is released. The solder is held above its re-flow temperature for several seconds to facilitate wetting of the substrate's metal protrusions and joining. Metal caps comprised of a noble metal such as palladium is applied to the surface of the metal bumps to prevent the metal bumps (which generally comprise a highly-conductive and highly-reactive metal such as copper) from oxidizing in the elevated temperatures just prior to and during the re-flow operation.